Method for the production of hydroxyalkyl polysiloxanes

ABSTRACT

The invention relates to a method for the production of hydroxyalkyl polysiloxanes of general formula (V) (SiO 4/2 ) k (R 1   2 SiO 3/2 ) m (R 1   2 SiO 2/2 ) p (R 1   3 SiO 1/2 ) q [O 1/2 SiR 3   2 13 (CR 4   2 ) b —OH] s [O 1/2 H] t  (V), wherein organosiloxanes of general formula (VI) (SiO 4/2 ) k (R 1 SiO 3/2 ) m (R 1   2 SiO 2/2 ) p (R 1   3 SiO 1/2 ) q [O 1/2 H] r (VI) containing silanol are made to react with compounds having at least one unit of general formula (IV) [O—(CR 4   2 )—SiR 3   2 ] n — (IV).

The present invention relates to a process for preparinghydroxyalkylpolysiloxanes.

[0001] Hydroxyalkylpolysiloxanes and hydroxyalkylsilicone resins areused in many applications, e.g. in the cosmetics and textile industries.However, the commercial use of these compounds on an even greater scaleis prevented by a relatively cumbersome production process. A knownmethod is direct hydrosilylation of protected or unprotected alkenols,e.g. allyl alcohol or hexenyl alcohol, with alpha,omega-H-siloxanes.Disadvantages of these processes are either the use of relativelyexpensive starting materials, e.g. platinum catalysts or hexenylalcohol, or the secondary reaction of hydrogen elimination which occursin the reaction catalyzed by noble metals and leads to hydrolyticallyunstable alkenyloxy end groups which can easily be cleavedhydrolytically with elimination of alkenols. To avoid this secondaryreaction, the alcohols used can be protected, but the protective grouphas to be removed in a further process step, which is costly.

[0002] EP-A-629648 describes a further process which starts out fromspecific cyclic silanes of the formula I which can react with HO—Sigroups (silanol groups) at the end of a silicone chain without the useof catalysts.

[0003] In this formula, R³ is a hydrocarbon radical having up to 20carbon atoms, R⁴ is hydrogen or a hydrocarbon radical having up to 20carbon atoms. These cyclic compounds can be reacted withsilanol-terminated siloxanes of the formula II

HO(R¹ ₂SiO)_(p)H   (II)

[0004] to give carbinol-terminated siloxanes of the formula III.

HO—(CR⁴ ₂)_(b)—SiR³ ₂O(R¹ ₂SiO)_(p)SiR³ ₂—(CR⁴ ₂)_(b)—OH   (III)

[0005] It is emphasized that the reaction without the use of catalystsis carried out at temperatures of from 25° C. to 150° C.

[0006] However, some problems are found in carrying out this reaction inpractice. Although the 6-membered ring with b=4 can be obtained instable form, it requires an elevated reaction temperature and quiteprolonged reaction times in the reaction with silanol end groups. The5-membered rings which are reactive for the purposes of EP-A-629648 canbe used in principle, but they are unstable substances and tend todecompose. The process described in EP-A-629648 is thus not verysuitable for industrial implementation.

[0007] It is therefore an object of the present invention to develop animproved process for preparing hydroxyalkylpolysiloxanes.

[0008] The invention accordingly provides a process for preparinghydroxyalkylpolysiloxanes of the formula V

(SiO_(4/2))_(k)(R¹SiO_(3/2))_(m)(R¹ ₂SiO_(2/2))_(p)(R¹₃SiO_(1/2))_(q)[O_(1/2)SiR³ ₂—(CR⁴ ₂)_(b)—OH]_(s)[O_(1/2)H]_(t)   (V),

[0009] in which silanol-containing organosiloxanes of the formula VI

(SiO_(4/2))_(k)(R¹SiO_(3/2))_(m)(R¹ ₂SiO_(2/2))_(p)(R¹₃SiO_(1/2))_(q)[O_(1/2)H]_(r)  (VI)

[0010] are reacted with compounds comprising at least one unit of theformula IV

—[O—(CR⁴ ₂)_(b)—SiR³ ₂)_(n)—  (IV)

[0011] where

[0012] R¹, R³, R⁴ are each a hydrogen atom or a monovalentC₁-C₂₀-hydrocarbon radical or C₁-C₁₅-hydrocarbonoxy radical which may beunsubstituted or substituted by —CN, —NCO, —NR^(x) ₂, —COOH, —COOR^(x),halogen, acryl, epoxy, —SH, —OH or —CONR^(x) ₂, in which one or morenonadjacent methylene units may be replaced by —O—, —CO—, —COO—, —OCO—,or —OCOO—, —S— or —NR^(x) groups and in which one or more nonadjacentmethine units may be replaced by —═, —N═N— or —P═ groups,

[0013] R^(x) is hydrogen or a C₁-C₁₀-hydrocarbon radical which may beunsubstituted or substituted by —CN or halogen,

[0014] b is at least 2,

[0015] s is at least 1,

[0016] r is at least 1,

[0017] n is at least 2,

s+t=r and

k+m+p+q is at least 2.

[0018] The invention is based on the recognition that linear siloxanesare also suitable for functionalizing Si—OH groups. If compoundscomprising units of the formula IV are used, these react readily andspecifically with silanol end groups to give carbinols in good yields.

[0019] Compounds comprising units of the formula IV are stable and canbe stored, and are therefore particularly well suited to use on anindustrial scale.

[0020] The C₁-C₂₀-hydrocarbon radicals and C₁-C₂₀-hydrocarbonoxyradicals R¹, R³, R⁴ may be aliphatically saturated or unsaturated,aromatic, linear or branched. R¹, R³, R⁴ preferably have from 1 to 12atoms, in particular from 1 to 6 atoms, preferably only carbon atoms orone alkoxy oxygen atom and otherwise only carbon atoms. R¹, R³, R⁴ arepreferably linear or- branched C₁-C₆-alkyl radicals. Particularpreference is given to the radicals methyl, ethyl, phenyl, vinyl andtrifluoropropyl.

[0021] Preference is given to preparing compounds of the formula V inwhich R³ is a methyl radical and R⁴ is hydrogen. b is preferably notmore than 50, in particular not more than 10. In a particularlypreferred embodiment, b is 3.

[0022] The hydroxy-functional organosiloxane of the formula VI may belinear, cyclic or branched. The sum of k, m, p, q, s and t is preferablyin the range from 2 to 20 000, in particular from 8 to 1000. To make areaction between the organosiloxane comprising units of the formula VIand the linear siloxane possible, the organosiloxane of the formula VIhas to contain hydroxy groups.

[0023] A preferred variant of an organosiloxane of the formula VI is alinear silicone polymer in which k and m are each 0, p is greater thanor equal to 1, q is 0 or 1 and r is 1 or 2, with the proviso that q=2−r.r is preferably equal to s. The preferred siloxanes of the formula VIcan have either a monomodal or multimodal distribution and can at thesame time have a narrow or very broad distribution.

[0024] A further preferred variant of a branched organosiloxane of theformula VI which can be used is an organosilicone resins. This can bemade up of a plurality of units, as indicated in the formula VI, withthe molar percentages of the units present being indicated by theindices k, m, p, q, r, s and t. Preference is given to from 0.1 to 20mol % of units r, based on the sum of k, m, p, q and r. At the sametime, however, k+m has to be >0. In the preparation of theorganosiloxane resin of the formula V, s has to be >0 and s+t has to beequal to r. Preference is given to preparing resins in which 5%<k+m<90%,based on the sum of k, m, p, q, s and t, and t is preferably equal to 0.In a particularly preferred case, the radical R³ is a methyl radical, R¹is a methyl radical and d is 3 and R⁴ is hydrogen.

[0025] As compounds comprising at least one unit of the formula IV,preference is given to using compounds of the formula VII

H—[O—(CR⁴ ₂)_(b)—SiR³ ₂]_(n)—O—X   (VII)

[0026] where

[0027] X is hydrogen or a C₁l-C₁₀-hydrocarbon radical which may beunsubstituted or substituted by —CN or halogen and

[0028] R³, R⁴, b and n are as defined above.

[0029] X is preferably hydrogen or a C₁-C₃-hydrocarbon radical, inparticular a methyl or ethyl radical.

[0030] Compounds of the formula VII in which X is hydrogen can dimerize.However, the dimers react in the same way as the monomers withorganosiloxanes of the formula VI.

[0031] As halogen substituents in the above formulae, preference isgiven to fluorine, chlorine and bromine.

[0032] The process can be carried out in the absence of catalysts,preferably at temperatures of from 0° C. to 150° C., preferably at least100° C. However, the process can be improved further by addingparticular catalysts. These catalysts are acidic or basic compounds andenable both the reaction times and the reaction temperatures to bereduced.

[0033] The catalyst used is an inorganic or organic Lewis acid or Lewisbase, and organic Brönsted acid or base, an organometallic compound or ahalide salt.

[0034] Preferred acids are carboxylic acids, partly esterifiedcarboxylic acids, in particular monocarboxylic acids, preferably formicacid or acetic acid, or unesterified or partly esterifiedmonophosphoric, oligophosphoric or polyphosphoric acids.

[0035] Preferred bases are alkylammonium hydroxides, ammonium alkoxides,alkylammonium fluorides or amine bases. Preferred organometallicreagents are organotin compounds, organozinc compounds or organotitaniumcompounds. Preferred salts are tetraalkylammonium fluorides.

[0036] Preference is given to phosphoric acids of the formula VIII

O═P(OR²)_(3-v)(OH)_(v)   (VIII)

[0037] where

[0038] R² is a substituted or unsubstituted, linear or branchedC₁-C₃₀-alkyl, C₂-C₄₀-alkenyl or -alkoxyalkyl, C₂-C₄₀-polyether,C₅-C₁₄-cycloalkyl or -aryl radical and

[0039] v is 0, 1 or 2.

[0040] After the functionalization reaction of the silanol groups, thecatalysts used are preferably deactivated by addition of anticatalystsor catalyst poisons before they can lead to cleavage of the Si—O—Sigroups. This secondary reaction is dependent on the catalyst used anddoes not necessarily occur, so that deactivation may also be able to beomitted. Examples of catalyst poisons are, for example, acids when basesare used and bases when acids are used, so that the ultimate effect is asimple neutralization reaction. The reaction product of catalyst andcatalyst poison can, depending on the use of the process product, eitherbe removed from the process product or remain in the process product.

[0041] In the process for preparing hydroxyalkylpolysiloxanes of theformula V, the amount of the compound containing units of the formula IVwhich is used depends on the amount r of the silanol groups to befunctionalized in the organosiloxane of the formula VI. However, ifcomplete functionalization of the OH groups is to be achieved, thecompound containing units of the formula IV is added in at leastequimolar amounts, based on n. If the compound containing units of theformula IV is used in excess, unreacted compound can subsequently eitherbe thermolytically decomposed and then distilled off or hydrolysed andthen, if appropriate, likewise distilled off.

[0042] If resins which have a defined carbinol content s+t are to beprepared, the stoichiometric ratios of resin to compound containingunits of the formula IV are chosen so that the desired carbinol contentis achieved. Remaining unreacted Si—OH groups can remain in theorganofunctional siloxane of the formula V or are, before or after thereaction with the compound containing units of the formula IV, reactedwith, for example, silazanes of the formula IX

[0043] where

[0044] R⁶ is hydrogen or a C₁-C₁₀-hydrocarbon radical which may beunsubstituted or substituted by —CN or halogen and

[0045] R⁷ is a C₁-C₁₀-hydrocarbon radical which may be unsubstituted orsubstituted by -CN or halogen.

[0046] The hydrocarbon radical R⁶ and R⁷ preferably have from 1 to 5carbon atoms. Particular preference is given to the radicals methyl,ethyl and vinyl. R⁷ is preferably hydrogen.

[0047] The process is preferably carried out at from 0° C. to 160° C.,particularly preferably from 40° C. to 100° C. The process can becarried out either in the presence of solvents or else without the useof solvents in suitable reactors. It may be carried out under reducedpressure or under superatmospheric pressure or at atmospheric pressure(0.1 MPa).

[0048] When solvents are used, preference is given to inert, inparticular aprotic solvents such as aliphatic hydrocarbons, e.g. heptaneor decane, and aromatic hydrocarbons, e.g. toluene or xylene. Etherssuch as THF, diethyl ether or MTBE can likewise be used. The amount ofsolvent should be sufficient to ensure sufficient homogenization of thereaction mixture. Solvents or solvent mixtures having a boiling point orboiling range up to 120° C. at 0.1 MPa are preferred.

[0049] The meanings of all the symbols used in the above formulae areindependent of one another.

[0050] In the following examples, unless indicated otherwise, allamounts and percentages are by weight, all pressures are 0.10 MPa (abs.)and all temperatures are 20° C. All viscosities were determined at 25°C.

EXAMPLE 1

[0051]1000 g of Me-siloxane (bishydroxy-terminated polydimethylsiloxanehaving an M_(n) of 3000 g/mol, determined by ¹H-NMR spectroscopy) werereacted at 80° C. with 79.4 g ofpoly(1,1-dimethyl-1-sila-2-oxacyclopentane) having a viscosity of 40mPas and 100 mg of formic acid. ¹H-NMR and ²⁹Si-NMR spectra showed thatafter 4 hours all OH groups had been converted into hydroxypropyl units.500 mg of triethylamine were subsequently added to the reaction solutionto deactivate the catalyst and the mixture was distilled briefly at 80°C. under reduced pressure (5 mbar). This left purebishydroxypropylpolydimethylsiloxane.

EXAMPLE 2

[0052] 1000 g of Me-siloxane (bishydroxy-terminated polydimethylsiloxanehaving an M_(n) of 3000 g/mol, determined by ¹H-NMR spectroscopy) werereacted at 80° C. with 77.6 g ofpoly(1,1-dimethyl-1-sila-2-oxacyclopentane) having a viscosity of 40mPas and 100 mg of formic acid. ¹H-NMR and ²⁹Si-NMR spectra showed thatafter 4 hours no Si—OH groups and nopoly(1,1-dimethyl-1-sila2-oxacyclopentane) were present. This gave 97%of the desired product bishydroxypropylpolydimethylsiloxane and 3% of apartially esterified formicacid-propylhydroxypropylpolydimethylsiloxane.

EXAMPLE 3

[0053] 1000 g of siloxane (bishydroxy-terminated polydimethylsiloxanehaving an M_(n) of 28 000 g/mol, determined by measurement of the OHnumber) were reacted at 80° C. with 8.4 g ofpoly(1,1-dimethyl-1-sila-2-oxacyclopentane) having a viscosity of 40mPas and 100 mg of Arlypon® (partly esterified phosphoric acid fromGrünau, Illertissen). ¹H-NMR and 29Si—NMR spectra showed that after 3hours all OH groups had been converted into hydroxypropyl units. 500 mgof triethylamine were subsequently added to the reaction solution todeactivate the catalyst and the mixture was distilled briefly at 80° C.under reduced pressure (5 mbar). This left purebishydroxypropylpolydimethylsiloxane.

EXAMPLE 4

[0054] 100 g of Me-siloxane (bishydroxy-terminated polydimethylsiloxanehaving an M_(n) of 1000 g/mol, determined by ¹H-NMR spectroscopy) werereacted at 80° C. with 23.4 g ofpoly(1,1-dimethyl-1-sila-2oxacyclopentane) having a viscosity of 40 mPasand 10 mg of Arlypon®. ¹H-NMR and ²⁹Si-NMR spectra showed that after 4hours all OH groups had been converted into hydroxypropyl units. 500 mgof triethylamine were subsequently added to the reaction solution todeactivate the catalyst and the mixture was distilled briefly at 80° C.under reduced pressure (5 mbar). This left purebishydroxypropylpolydimethylsiloxane.

EXAMPLE 5

[0055] 1000 g of silicone oil (bishydroxy-terminatedpolydimethylsiloxane having a vinyl:methyl ratio of 1:4 and an M_(n) of2800 g/mol, determined by 1H-NMR spectroscopy) were reacted at 80° C.with 83.2 g of poly(1,1-dimethyl-1-sila-2-oxacyclopentane) having aviscosity of 60 mPas and 100 mg of formic acid. ¹H-NMR and ²⁹Si-NMRspectra showed that after 3 hours all OH groups had been converted intohydroxypropyl units. 500 mg of triethylamine were subsequently added tothe reaction solution to deactivate the catalyst and the mixture wasdistilled briefly at 80° C. under reduced pressure (5 mbar). This leftpure bishydroxypropylpolydimethylsiloxane.

EXAMPLE 6

[0056] 100 g of silicone oil (bishydroxy-terminated polydimethylsiloxanehaving a trifluoropropyl:methyl ratio of 1:1 and an M_(n) of 900 g/mol,determined by ¹H-NMR spectroscopy) were reacted at 80° C. with 26.0 g ofpoly(1,1-dimethyl-1-sila-2-oxacyclopentane) having a viscosity of 60mPas and 10 mg of formic acid. ¹H-NMR and ²⁹Si-NMR spectra showed thatafter 3 hours all OH groups had been converted into hydroxypropyl units.500 mg of triethylamine were subsequently added to the reaction solutionto deactivate the catalyst and the mixture was distilled briefly at 80°C. under reduced pressure (5 mbar). This left purebishydroxypropylpolydimethylsiloxane.

EXAMPLE 7

[0057] 100 g of monohydroxy-terminated polydimethylsiloxane having anM_(n) of 3000 g/mol, determined by ¹H-NMR spectroscopy, were reacted at80° C. with 3.9 g of poly(1,1-dimethyl-1-sila-2-oxacyclopentane) havinga viscosity of 110 mPas and 10 mg of Arlypon® (partly esterifiedphosphoric acid from Grünau, Illertissen). ¹H-NMR and ²⁹Si-NMR spectrashowed that after 3 hours all OH groups had been converted intohydroxypropyl units and no broadening of the molecular weightdistribution was discernible. 500 mg of triethylamine were subsequentlyadded to the reaction solution to deactivate the catalyst and themixture was distilled briefly at 80° C. under reduced pressure (5 mbar).This left pure monohydroxypropylpolydimethylsiloxane.

EXAMPLE 8

[0058] 100 g of monohydroxy-terminated polydimethylsiloxane having anM_(n) of 3000 g/mol, determined by ¹H-NMR spectroscopy, were reacted at80° C. with 3.9 g of poly(1,1-dimethyl-1-sila-2-oxacyclopentane) havinga viscosity of 110 mPas and 50 mg of benzyltrimethylammonium hydroxide(40% strength solution in methanol). ¹H-NMR and ²⁹Si-NMR spectra showedthat after 4 hours all OH groups had been converted into hydroxypropylunits and no broadening of the molecular weight distribution wasdiscernible. 500 mg of triethylamine were subsequently added to thereaction solution to deactivate the catalyst and the mixture wasdistilled briefly at 80° C. under reduced pressure (5 mbar). This leftpure monohydroxypropylpolydimethylsiloxane.

1. A process for preparing hydroxyalkylpolysiloxanes of the formula V(SiO_(4/2))_(k)(R¹SiO_(3/2))_(m)(R¹ ₂SiO_(2/2))_(p)(R¹₃Si_(1/2))_(q)([O_(1/2)SiR³ ₂—(CR⁴ ₂)_(b)—OH]_(s)[O_(1/2)H]_(t)   (V),in which silanol-containing organosiloxanes of the formula VI(SiO_(4/2))_(k)(R¹SiO_(3/2))_(m)(R¹ ₂SiO_(2/2))_(p)(R¹₃SiO_(1/2))_(q)[O_(1/2)H]_(r)   (VI) are reacted with compoundscomprising at least one unit of the formula IV —[O—(CR⁴ ₂)_(b)—SiR³₂)_(n)—  (IV) where R¹, R³, R⁴ are each a hydrogen atom or a monovalentC₁-C₂₀-hydrocarbon radical or C₁-C,₅-hydrocarbonoxy radical which may beunsubstituted or substituted by —CN, —NCO, —NR^(x) ₂, —COOH, —COOR^(x),halogen, acryl, epoxy, —SH, —OH or —CONR^(x) ₂, in which one or morenonadjacent methylene units may be replaced by —O—, —CO—, —COO—, —OCO—,or —OCOO—, —S— or —NR^(x)— groups and in which one or more nonadjacentmethine units may be replaced by —N═, —N═N— or —P═ groups, R^(x) ishydrogen or a C₁-C₁₀-hydrocarbon radical which may be unsubstituted orsubstituted by —CN or halogen, b is at least 2, s is at least 1, r is atleast 1, n is at least 2, s+t=r and k+m+p+q is at least
 2. 2. Theprocess as claimed in claim 1, in which R¹ is methyl, ethyl, phenyl,vinyl or trifluoropropyl.
 3. The process as claimed in claim 1 or 2, inwhich R⁴ is hydrogen.
 4. The process as claimed in any of claims 1 to 3,in which R³ is a methyl radical.
 5. The process as claimed in any ofclaims 1 to 4, in which a linear organosiloxane of the formula VI inwhich k and m are each 0, p is greater or equal to 1, q is 0 or 1 and ris 1 or 2 is used.
 6. The process as claimed in any of claims 1 to 4, inwhich resins in which 5%<k+m<90%, based on the sum of k, m, p, q, s andt, are prepared.
 7. The process as claimed in any of claims 1 to 6, inwhich the reaction temperature is from 0° C. to 160° C.
 8. The processas claimed in any of claims 1 to 7, in which a catalyst which is aninorganic or organic Lewis acid or Lewis base is used.
 9. The process asclaimed in claim 8, in which the catalyst is selected from amongcarboxylic acids, partly esterified carboxylic acids, unesterified andpartly esterified monophosphoric, oligophosphoric and polyphosphoricacids, alkylammonium hydroxides, ammonium alkoxides, alkylammoniumfluorides and amine bases.